1. Field of the Invention
The present invention relates generally to enhancing the safety and security of manufacturing processes and, particularly, to simultaneously monitoring and exercising control over access to enclosed areas which house operating machinery or the like. More specifically, the present invention is directed to mechanisms which may prevent the opening of and/or monitor the state of access doors and, especially, to mechanisms of such type which are suitable for mounting on access doors so as to be operable by handles provided on such doors. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in manufacturing facilities having enclosed areas in which, due to safety considerations, unattended operations are performed. Such an area may, for example, house machinery or machine elements which should not be approached by plant personnel while in operation. The doors or openings through which access to such areas is obtained are customarily provided with guard locking devices which include a door status signal generator, i.e., an electrical switch, located on an interior wall of the secure area adjacent to the access door. These previous guard locking devices, which are also generally known in the art as "safety switches", perform both of the functions of door locking and controlling the state of the status signal generator. The prior art "safety switches" have conventionally included pivotal actuators coupled to rotatable door handles. Pivotal actuators have the disadvantage that they are not suitable for use on sliding doors. Pivotal actuators also have the disadvantage that the force transmitted thereby during door handle operation is not uniform, i.e., latching of the door occurs with increasing clamping force on the fixed part of the door-locking mechanism and this non-uniform force will not reliably result in establishment of operational contact with the associated status signal generator. There has, accordingly, been a long-standing desire and need in the art for a universal monitoring/locking mechanism suitable for controlling and monitoring the state of both pivotally mounted and sliding access doors while being characterized by uniform force transmission.